Download GTU (Gujarat Technological University) BE/BTech (Bachelor of Engineering / Bachelor of Technology) 2019 Summer 5th Sem New 2150503 Chemical Engineering Thermodynamics Ii Previous Question Paper
Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ?V (NEW) EXAMINATION ? SUMMER 2019
Subject Code: 2150503 Date: 31/05/2019
Subject Name: Chemical Engineering Thermodynamics - II
Time: 02:30 PM TO 05:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
Q.1 (a) Discuss the phase rule and Duhem?s theorem. 03
(b) Derive the expression of vapor composition at equilibrium using flash
vaporization.
04
(c) Derive the equation for criteria for phase equilibrium in terms of chemical
potential for a mixture of N components and ? phases.
07
Q.2 (a) At 303 K the vapour pressures of benzene (1) and toluene (2) are 15.75 kPa and
4.89 kPa respectively. Determine the partial pressure and composition of the
benzene vapour in equilibrium with a liquid mixture consisting of equal weight
of the two components.
03
(b) A 30 mol% methanol-water solution is to be prepared. How many cubic meters
of pure methanol (molar volume 40.727 x 10
-6
m
3
/mol) and pure water (molar
volume 18.068 x 10
-6
m
3
/mol) are to be mixed to prepare 2 m
3
of the desired
solution? The partial molar volumes of methanol and water in 30% solution are
38.632 x 10
-6
m
3
/mol and 17.765 x 10
-6
m
3
/mol respectively.
04
(c) Define fugacity coefficient. Discuss any two methods to evaluate fugacity
coefficient in details.
07
OR
(c) Water (1)/hydrazine (2) system forms an azeotrope containing 58.5 mol%
hydrazine at 393 K and 101.3 kPa. Calculate the equilibrium vapor composition
for a solution containing 20 mol% hydrazine. The relative volatility of water
with reference to hydrazine is 1.6 and may be assume to remain constant in the
temperature range involved. Vapor pressure of hydrazine at 393 K is 124.76
kPa.
07
Q.3 (a) Derive the Margules equations from the following expression:
21 1 12 2
12
E
G
A x A x
xx RT
??
03
(b) Define partial molar properties and explain any one method in detail for
evaluation of partial molar properties.
04
(c) The following values refer to the Wilson parameters for the system of acetone
(1)/water (2): a12 = 1225.31 J/mol, a21 = 6051.01 J/mol, V1 = 74.05 x 10
?6
m
3
/mol and V2 = 18.07 x 10
?6
m
3
/mol. The vapour pressures are given by the
equations:
12
2795.817 3799.887
ln 14.3915 and ln 16.262
43.198 46.854
sat sat
PP
TT
? ? ? ?
??
where pi
sat
is in kPa and T is in K. Calculate the equilibrium pressure and
composition of vapour in equilibrium with a liquid of composition x 1 = 0.43 at
349 K.
07
OR
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1
Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ?V (NEW) EXAMINATION ? SUMMER 2019
Subject Code: 2150503 Date: 31/05/2019
Subject Name: Chemical Engineering Thermodynamics - II
Time: 02:30 PM TO 05:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
Q.1 (a) Discuss the phase rule and Duhem?s theorem. 03
(b) Derive the expression of vapor composition at equilibrium using flash
vaporization.
04
(c) Derive the equation for criteria for phase equilibrium in terms of chemical
potential for a mixture of N components and ? phases.
07
Q.2 (a) At 303 K the vapour pressures of benzene (1) and toluene (2) are 15.75 kPa and
4.89 kPa respectively. Determine the partial pressure and composition of the
benzene vapour in equilibrium with a liquid mixture consisting of equal weight
of the two components.
03
(b) A 30 mol% methanol-water solution is to be prepared. How many cubic meters
of pure methanol (molar volume 40.727 x 10
-6
m
3
/mol) and pure water (molar
volume 18.068 x 10
-6
m
3
/mol) are to be mixed to prepare 2 m
3
of the desired
solution? The partial molar volumes of methanol and water in 30% solution are
38.632 x 10
-6
m
3
/mol and 17.765 x 10
-6
m
3
/mol respectively.
04
(c) Define fugacity coefficient. Discuss any two methods to evaluate fugacity
coefficient in details.
07
OR
(c) Water (1)/hydrazine (2) system forms an azeotrope containing 58.5 mol%
hydrazine at 393 K and 101.3 kPa. Calculate the equilibrium vapor composition
for a solution containing 20 mol% hydrazine. The relative volatility of water
with reference to hydrazine is 1.6 and may be assume to remain constant in the
temperature range involved. Vapor pressure of hydrazine at 393 K is 124.76
kPa.
07
Q.3 (a) Derive the Margules equations from the following expression:
21 1 12 2
12
E
G
A x A x
xx RT
??
03
(b) Define partial molar properties and explain any one method in detail for
evaluation of partial molar properties.
04
(c) The following values refer to the Wilson parameters for the system of acetone
(1)/water (2): a12 = 1225.31 J/mol, a21 = 6051.01 J/mol, V1 = 74.05 x 10
?6
m
3
/mol and V2 = 18.07 x 10
?6
m
3
/mol. The vapour pressures are given by the
equations:
12
2795.817 3799.887
ln 14.3915 and ln 16.262
43.198 46.854
sat sat
PP
TT
? ? ? ?
??
where pi
sat
is in kPa and T is in K. Calculate the equilibrium pressure and
composition of vapour in equilibrium with a liquid of composition x 1 = 0.43 at
349 K.
07
OR
2
Q.3 (a) Discuss the area test for checking the consistency of experimental VLE data. 03
(b) The experimental pressure-volume data for benzene at 675 K from a very low
pressures up to 75 bar may be approximated by the equation V = 0.0554(1/P -
0.0046).Where V is in m
3
/mol and pressure P is in bar. What is the fugacity of
benzene at 1 bar and 675 K?
04
(c) What is gamma-phi formulation of VLE? Draw block diagrams for the BUBL
P and DEW P calculations. Write all necessary equations.
07
Q.4 (a) Write a short note on group contribution methods. 03
(b) Define azeotrope and explain the minimum boiling and maximum boiling
azeotropes with suitable examples.
04
(c) Prove ?Henry?s law applies to a species as it approaches infinite dilution in a
binary solution, and the Gibbs/Duhem equation ensures the validity of the
Lewis/Randall rule for the other species as it approaches purity.
07
OR
Q.4 (a) Explain the Lewis-Randall rule and its significance. 03
(b) Write a brief note on retrograde condensation and its application. 04
(c) Using fundamental properties relations establish the expression of standard
Gibbs free energy change of chemical reaction as a function of thermodynamic
equilibrium constant.
07
Q.5 (a) Write down Raoult's Law and Henry's Law explaining each term associated
with them with their applicability.
03
(b) Explain T-x-y diagram for partial miscible system. 04
(c) For an ideal gas, the exact mathematical expressions can be developed for the
effect of T and P on the reaction co-ordinate at equilibrium. For conciseness we
let
? ?
i
v
i
yK ?
?
. Then we can write the mathematical relations:
and
yy
e e e
PT yy
PT
KK
d d
T T dK T T dK
? ? ? ?
?? ? ? ? ? ?? ? ? ? ?
??
? ? ? ? ? ? ? ?
? ? ? ?
? ? ? ?
? ? ? ?
Using above equations, show that
0
2
)
y
e
P y
K
d
iH
T RT dK
? ? ? ??
??
??
?
??
and ) ( )
y
ee
T y
K
d
ii v
T P dK
?? ? ??
??
??
?
??
07
OR
Q.5 (a) Write a brief note on solid - vapor equilibrium. 03
(b) The ammonia synthesis reaction written as: 0.5 N2(g) + 1.5 H2(g) ? NH3(g) with
0.5 mol nitrogen and 1.5 mol hydrogen as the initial amounts of reactants and
with the assumption that the equilibrium mixture is an ideal gas, show that:
?e = 1 ? (1+1.299KP)
?0.5
04
(c) Estimate the equilibrium constant at 1000 K and 0.1 MPa for the reaction :
CO2(g) + H2(g) ? CO(g) + H2O(g) taking into account the variation of ?H? with
temperature.
Component a b ? 10
3
e ?10
-5
?G?298
(J/mol)
?H?298
(J/mol)
CO2 45.369 8.688 -9.619 -394359 -393509
H2 27.012 3.509 0.690 - -
CO 28.068 4.631 -0.258 -137169 -110525
H2O 28.85 12.055 1.006 -228572 -241818
07
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This post was last modified on 20 February 2020